Include the notification_referrer_id for better UI

[Orrison]

In the actual Github notifications page, links to the notifications will include at notification_referrer_id. This provides a nice little bar at the top to perform some actions on the notification.
It would be great if Gitify would include this in it's links so functionality is similar to the native notifications page, and we get that bar at the top.

[bevanjkay]

@manosim The notification_referrer_id seems to be a base64 encoded string made up of

018:NotificationThread${notification.id}:${userID}

I don't believe the user's ID is being stored anywhere at present?

[codebytere]

Got this working locally, i'll try to have a PR up in a few days when i have time to clean it up and add tests!

[jasonbarry]

A downside of including the notification_referrer_id query param is that clicking a notification in Gitify will always open a new tab, even if the issue / pull request is already open. If the notification_referrer_id query param wasn't present, then the URL of the notification in Gitify would match the URL of the already-open tab, and the browser would reload the existing tab and give it focus.

In my opinion, I'd prefer if the browser opened the already existing tab, to help reduce the amount of open tabs in a given window.